Appendix E - Stormwater Management Plan

•     Minor runoff from Southern Basin directed to Central WQCP – 63% AEP peak flows from the Southern Bioretention
      Basin (will be directed to the Central WQCP to increase turnaround time (Hydraulic Residence Time) of the Pond and
      for peak flow attenuation. This has been modelled in MUSIC by using primary drainage link to direct runoff below the
      63% AEP storm event (<1.25m3/s) to the “Central WQCP” (not modelled in MUSIC) and a secondary drainage link to
      direct runoff high-flows downstream of the Pond.

•     Minor runoff (63% AEP peak flow) from Catchment B1 and B2 to Central Bioretention Basin – peak flows in the 63%
      AEP storm event will be directed towards the GPT and Central Bioretention Basin for stormwater quality treatment
      before discharging to the proposed WQCP (not modelled in MUSIC). High flows bypassing the Central Bioretention
      Basin will be directed into the WQCP. This has been modelled in MUSIC by using primary drainage link to direct
      runoff below the 63% AEP storm event (<0.29m3/s) to the Central Bioretention Basin and a secondary drainage link
      to direct high-flows to the towards the proposed WQCP (not modelled in MUSIC).

A layout of the primary and secondary drainage links modelled is indicated on the MUSIC configuration layout provided in
Appendix F. Drawing No. B14158.W-SK102 also provides further details of the site’s internal drainage strategy.

No routing was adopted for drainage links within MUSIC model in accordance with Section 4.17 of the MUSIC Modelling
Guidelines (2010). This assumes flows and associated pollutants from all parts of the catchment arrive at the treatment
nodes at the same time. This is conservative as it means that MUSIC may overestimate the overflow volumes.

4.4.4       TREATMENT NODES

4.4.4.1 BIORETENTION TREATMENT NODE

Bioretention treatment nodes were used to model the proposed bioretention filter in the northern and southern basin and
bio-pod. Default K and C* values were adopted for these treatment nodes. These treatment nodes were set up generally
in accordance with the MUSIC Modelling Guidelines (2010) and Interim MUSIC Bioretention Treatment Node (2013).
Refer to Table 4-2 for the bioretention treatment node configuration. All other parameters have been adopted from
MUSIC Modelling Guidelines (2010).

                                   Table 4-2:       Bioretention Basin Modelled Parameters

              Parameter                Northern Basin      Central Basin     Southern Basin         Pod D2        Pod D3
    Filter Media Area (m2)                   525                 650               305               75            75
    Surface Area (m2)                        525                 650               340               75            75
    Extended Detention Depth (m)             0.3                 0.3               0.3               0.2           0.2
    Filter Depth (m)                         0.4                 0.4               0.4               0.4           0.4
                                                                                                    Sandy         Sandy
    Filter Media Type                   Sandy Loam          Sandy Loam        Sandy Loam
                                                                                                    Loam          Loam
    Saturated Hydraulic
    Conductivity of Filter Media             200                 200               200               200           200
    (mm/hr)
    TN Content of Filter Media
                                             400                 400               400               400           400
    (mg/kg)
    Orthophosphate Content of
                                              30                 30                 30                30            30
    Filter Media (mg/kg)
    Overflow Weir Width Modelled
                                                4                 5                 6                2.4           2.4
    (m)1
                               1The width of the major overflow weir was conservatively modelled.

               Refer to Drawing No. B14158.W-SK102 and SK113 in Appendix G for further treatment train details.

          Since the Issue A report, Table 4-2 has been updated to incorporate the approved stormwater quality
          management strategy, as agreed with Council. Refer to Appendix I for correspondence with Council.




16-001014-01B | STORMWATER MANAGEMENT PLAN                            COOROY RETIREMENT COMMUNITY, TRADING POST
(SWMP) | PALM LAKE RESORTS                                                                        ROAD, COOROY             | 19